I think for Nintendogs to work on Wii it needs Wii Speak and WM+, maybe even optional balance board. All of those will be out in a mass way by 09's holiday season so.... Nintendogs as a '09 holiday release would make a lot of sense and help further boost Wii Speak and WM+ sales too.
Now where is the Pokemon MMO for Wii?? Those two out for Christmas would be HUGE beyond even what another Zelda and Mario could do combined.